Tumbler base



FIG. 1 is a perspective view of my new, original and ornamental design for a tumbler base;

FIG. 2 is a top plan view thereof;

FIG. 3 is a front plan view thereof;

FIG. 4 is a rear plan view thereof;

FIG. 5 is a right plan view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is left plan view thereof. 

The ornamental design for a tumbler base, substantially as shown. 